.TH std::ranges::next 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::ranges::next \- std::ranges::next

.SH Synopsis
   Defined in header <iterator>
   Call signature
   template< std::input_or_output_iterator I >                        \fB(1)\fP \fI(since C++20)\fP
   constexpr I next( I i );
   template< std::input_or_output_iterator I >                        \fB(2)\fP \fI(since C++20)\fP
   constexpr I next( I i, std::iter_difference_t<I> n );
   template< std::input_or_output_iterator I, std::sentinel_for<I> S
   >                                                                  \fB(3)\fP \fI(since C++20)\fP
   constexpr I next( I i, S bound );
   template< std::input_or_output_iterator I, std::sentinel_for<I> S
   >                                                                  \fB(4)\fP \fI(since C++20)\fP
   constexpr I next( I i, std::iter_difference_t<I> n, S bound );

   Return the n^th successor of iterator i.

   The function-like entities described on this page are niebloids, that is:

     * Explicit template argument lists cannot be specified when calling any of them.
     * None of them are visible to argument-dependent lookup.
     * When any of them are found by normal unqualified lookup as the name to the left
       of the function-call operator, argument-dependent lookup is inhibited.

   In practice, they may be implemented as function objects, or with special compiler
   extensions.

.SH Parameters

   i     - an iterator
   n     - number of elements to advance
   bound - sentinel denoting the end of the range i points to

.SH Return value

   1) The successor of iterator i.
   2) The n^th successor of iterator i.
   3) The first iterator equivalent to bound.
   4) The n^th successor of iterator i, or the first iterator equivalent to bound,
   whichever is first.

.SH Complexity

   1) Constant.
   2) Constant if I models std::random_access_iterator; otherwise linear.
   3) Constant if I and S models both std::random_access_iterator<I> and
   std::sized_sentinel_for<S, I>, or if I and S models std::assignable_from<I&, S>;
   otherwise linear.
   4) Constant if I and S models both std::random_access_iterator<I> and
   std::sized_sentinel_for<S, I>; otherwise linear.

.SH Possible implementation

   struct next_fn
   {
       template<std::input_or_output_iterator I>
       constexpr I operator()(I i) const
       {
           ++i;
           return i;
       }

       template<std::input_or_output_iterator I>
       constexpr I operator()(I i, std::iter_difference_t<I> n) const
       {
           ranges::advance(i, n);
           return i;
       }

       template<std::input_or_output_iterator I, std::sentinel_for<I> S>
       constexpr I operator()(I i, S bound) const
       {
           ranges::advance(i, bound);
           return i;
       }

       template<std::input_or_output_iterator I, std::sentinel_for<I> S>
       constexpr I operator()(I i, std::iter_difference_t<I> n, S bound) const
       {
           ranges::advance(i, n, bound);
           return i;
       }
   };

   inline constexpr auto next = next_fn();

.SH Notes

   Although the expression ++x.begin() often compiles, it is not guaranteed to do so:
   x.begin() is an rvalue expression, and there is no requirement that specifies that
   increment of an rvalue is guaranteed to work. In particular, when iterators are
   implemented as pointers or its operator++ is lvalue-ref-qualified, ++x.begin() does
   not compile, while ranges::next(x.begin()) does.

.SH Example


// Run this code

 #include <cassert>
 #include <iterator>

 int main()
 {
     auto v = {3, 1, 4};
     {
         auto n = std::ranges::next(v.begin());
         assert(*n == 1);
     }
     {
         auto n = std::ranges::next(v.begin(), 2);
         assert(*n == 4);
     }
     {
         auto n = std::ranges::next(v.begin(), v.end());
         assert(n == v.end());
     }
     {
         auto n = std::ranges::next(v.begin(), 42, v.end());
         assert(n == v.end());
     }
 }

.SH See also

   ranges::prev    decrement an iterator by a given distance or to a bound
   (C++20)         (niebloid)
   ranges::advance advances an iterator by given distance or to a given bound
   (C++20)         (niebloid)
   next            increment an iterator
   \fI(C++11)\fP         \fI(function template)\fP
